Proliferation of high-speed wireless local area network (WLAN) access points combined with the availability of a wide variety of digital file-based content provides the opportunity for users to receive this content wirelessly at WLAN enabled media playback devices. These devices include portable devices specifically purposed for media playback such as portable MP3 or MPEG video players, Personal Digital Assistants (PDAs), laptop computers, GPS devices, and mobile automotive installed media players. Portable and mobile automotive media playback devices use either flash memory or hard disk drives to store the file-based content, and are battery powered. The file-based digital media available for transfer to portable or mobile automotive players includes for example navigation information (maps and street addresses) to be used in conjunction with GPS receivers, and entertainment content including audio (MP3, .wav, or other formats) and video (MPEG-2, MPEG-4, etc.) files.
Currently, media playback devices such as those listed above typically receive new content when a user couples and activates such devices to a source of new content, such as a personal computer (PC). For example, the iPod®, provided by Apple Computer, Inc. of Cupertino, Calif., receives new digital audio files via a USB 2.0 connection to a Macintosh or Windows PC. The user may couple the iPod to the computer and activates synchronization using iTunes® media management software. Typically, the user activates the synchronization after they have manually acquired new audio content, either by purchasing the content from an online service or by encoding audio tracks from an audio Compact Disc (CD).
One convenient system for transferring content to portable or mobile automotive player devices is to attach wireless LAN transceivers to the portable devices and execute synchronization automatically when the portable device is in range of the WLAN and when new content is available at a server coupled to the WLAN for synchronization. It would be convenient, for example, if a PDA could be left in a brief case and synchronization would occur automatically. Or, another convenient mode of operation would be provide the user with the capability to trigger the synchronization from the PC. Further convenience would be realized if a mobile automotive media playback device permanently installed in a car could synchronize wirelessly when in range of the WLAN and when new content is available to be transferred, and likewise when a user triggered the synchronization at the PC. However, current hardware and software designs for portable or mobile automotive media playback devices require the devices to be constantly attached to the WLAN for the above-described automatic or user-triggered synchronization to occur.
A portable or mobile automotive device that is available on a wireless network for a substantially long period may require a significant portion of the electronics of the portable player device to be functioning. Although there are many digital wireless protocols, the 802.11 (802.11b, g, a) protocols have proliferated in the market and are very low in cost. Devices that use 802.11WLAN transceivers typically use an operating system with a Transmission Control Protocol/Internet Protocol (TCP/IP) software stack, therefore the processor and operating system must be fully functional for the TCP/IP software to function. For example, a mobile automotive device incorporating an ARM7 microprocessor running Linux, and an 802.11b WLAN transceiver uses more than 200 milliamps when active on the network. For battery-powered devices, this amount of energy usage would drain the battery after a short while.
One solution for maintaining usable battery power in a portable player device would be to place the portable device in a docking/charging station. However, this is inconvenient for the user since they have to remember to place the portable device in the dock. And it would be expensive, if not cost prohibitive, to couple a mobile automotive media player to a constant source of AC power.